NCDC added Alaska climate divisions to its nClimDiv dataset on Friday, March 6, 2015, coincident with the release of the February 2015 monthly monitoring report. For more information on this data, please visit the Alaska Climate Divisions FAQ.

On a broad scale, the 1980s and 1990s were characterized by unusual wetness with short periods of extensive droughts, the 1930s and 1950s were characterized by prolonged periods of extensive droughts with little wetness, and the first decade of the 2000s saw extensive drought and extensive wetness
(moderate to extreme drought graphic,
severe to extreme drought graphic).

there were two epicenters of extreme (D3) to exceptional (D4) drought within this large moderate to severe (D2) drought area — one located in the California-Nevada-Oregon region and the other in the Southern Plains centered in northern Texas and adjacent Oklahoma; and

Percent area of the CONUS in moderate to exceptional drought, January 4, 2000 to present, based on the U.S. Drought Monitor.

Palmer Drought Index

The Palmer drought indices measure the balance between moisture demand (evapotranspiration driven by temperature) and moisture supply (precipitation). The Palmer Z Index depicts moisture conditions for the current month, while the Palmer Hydrological Drought Index (PHDI) and Palmer Drought Severity Index (PDSI) depict the current month's cumulative moisture conditions integrated over the last several months.
While both the PDSI and PHDI indices show long-term moisture conditions, the PDSI depicts meteorological drought while the PHDI depicts hydrological drought. The PDSI map shows less severe and extensive drought in the West and parts of the Plains than the PHDI map because the meteorological conditions that produce drought are not as long-lasting as the hydrological impacts.

Standardized Precipitation Index

The Standardized Precipitation Index (SPI) measures moisture supply. The SPI maps here show the spatial extent of anomalously wet and dry areas at time scales ranging from 1 month to 24 months.

The SPI maps illustrate how moisture conditions have varied considerably through time and space over the last two years.
Dryness across parts of the Northern Plains to Northeast is evident in February and the last 2 to 3 months and even extends as far back as 6 months.
Much of the Central Plains to Mid-Atlantic States has been dry, especially at the 2 to 3 month time scale.
Dryness along the Gulf of Mexico Coast has been acute during February and the last 6 to 9 months.
The West Coast (except California's interior valleys) received enough precipitation in February and December, and earlier, to register as near-normal on the February and 3 to 12 month SPI maps, but January dryness is behind the widespread dry conditions across the West at 2 months. Great Basin dryness is evident at the 1 to 6-month time scales.
The long-term dryness in the West and Southern Plains shows up at the 24-month time scale.

Standardized Precipitation Evapotranspiration Index

The SPI measures water supply (precipitation), while the SPEI (Standardized Precipitation Evapotranspiration Index) measures the combination of water supply (precipitation) and water demand (evapotranspiration as computed from temperature). Warmer temperatures tend to increase evapotranspiration, which generally makes droughts more intense.

1-month SPEI for current month.

1-month SPI for current month.

Temperatures were unusually warm in the West during February. In winter when temperatures are normally low, the effect of the warm temperature anomalies is usually muted, but the magnitude of the record warm February temperatures made a noticeable difference in the SPEI and SPI.
When the entire year is considered, the record warm temperatures in the West significantly intensified drought conditions when the 12-month SPEI is compared to the SPI. The unusual western warmth of the last several years contributed to more intense drought on the SPEI maps compared to the SPI maps at longer time scales.

48-month SPEI for current month.

48-month SPI for current month.

Agricultural, Hydrological, and Meteorological Indices and Impacts

USDA western states mountain snowpack

USGS monthly streamflow percentiles

Drought conditions were reflected in numerous agricultural, hydrological, and other meteorological indicators, both observed and modeled.

Regional Discussion

Hawaii:February 2015 was drier than normal across much of Hawaii. The last 2 to 3 months have been much drier than normal across the state. Even with the rainfall from October 2014 and earlier, the last 5, 6, and 8 months averaged drier than normal at most stations. The precipitation anomaly pattern was mixed at 11 to 12 and even 24 months, but dryness was dominant at 36 months.
The dryness was reflected in below-normal streamflow on some of the islands.
On the USDM map, moderate drought expanded to cover more than half (53.9 percent) of the state, reflecting the persistently low precipitation as well as the continued low reservoir situation in central Molokai and the Upcountry Maui area.

Puerto Rico:February continued a drier-than-normal trend for north-central Puerto Rico. The drier-than-normal area becomes bigger and extends further south and east at the longer time scales (last 2, 3, 5, 6 months).
On the March 3rd USDM map, abnormal dryness continued for a sixth (16.6 percent) of Puerto Rico.

Percent area of the Western U.S. in moderate to extreme drought, January 1900 to present, based on the Palmer Drought Index.

As noted above, dry weather has dominated the West for much of the last three years, resulting in significant hydrological (low lake, reservoir, and stream levels) and agricultural impacts. According to the USDM, 59.8 percent of the West was experiencing moderate to exceptional drought at the end of February, which is an increase compared to the previous month. The Palmer Drought Indexpercent area statistic for the West was 45.0 percent, an increase of about 10 percent compared to the previous month.

Nevada and Utah were an epicenter of dryness during February 2015, as seen in the SPI map. Based on precipitation (e.g., SPI) alone, the state ranks for February 2015 were 38th driest for Nevada and 29th driest for Utah. Utah had the warmest February on record and Nevada the second warmest. When temperature is also taken into account, both Nevada and Utah had the driest February on record, based on the SPEI. For Nevada, the year-to-date ranked as the 17th driest January-February (based on precipitation) but warmest (based on temperature) on record, and this difference is evident when the SPI (24th driest) is compared to the SPEI (driest).

October marks the start of the growing season for the Primary Hard Red Winter Wheat agricultural belt. While portions of the region were drier than normal this month, February 2015 ranked in the middle of the 1895-2015 record for precipitation at 56th driest, and 52nd coolest for temperature, regionwide. The growing season to date ranked as the 60th driest and 37th warmest October-February in the 120-year record. The last three growing season-to-date periods have averaged slightly drier than normal, regionwide.

NOAA Regional Climate Centers:

A more detailed drought discussion, provided by the NOAA Regional Climate Centers and others, can be found below.

As described by the High Plains Regional Climate Center, this month, there was a large contrast in temperatures across the United States due to a ridge to the west and a trough to the east. The extreme warmth in the west was a concern due to the continued low snowpack and the cold in the east allowed for wintry weather to impact locations even in the Deep South. Because the High Plains region was on the dividing line of the warm and cold air, eastern areas were below normal, central areas were near normal, and western areas were above normal.

After a fairly dry January, precipitation returned in February for some areas of the High Plains region, especially along the Front Range in Colorado, areas of central Wyoming, and portions of Kansas, Nebraska, and North Dakota. There were dry areas of the region as well, including South Dakota, southern Kansas, southwestern Wyoming, and portions of eastern North Dakota and northwestern Colorado where precipitation totaled 50 percent of normal, at best. A few isolated areas received little to no precipitation and ranked in the top 10 driest Februaries on record. At this time of the year, precipitation does not contribute a large percentage of the annual total; however, dry areas will need to be monitored this spring when deficits can grow more quickly.

Although typically a quiet time of the year for drought developments/improvements in the High Plains region, drought conditions expanded over the past month, according to the latest releases of the USDM. The total area in drought (D1-D4) increased from about 12 percent to just over 20 percent with moderate drought conditions (D1) expanding across western Colorado and into southern Wyoming. A combination of unseasonably warm weather and a low snow water equivalent in the mountain snowpack has led to this depiction on the USDM. For the region as a whole, this expanded the total D1 coverage from about 7 percent to 15 percent. The remaining severe (D2) and extreme (D3) drought conditions in portions of eastern Colorado and western and southern Kansas remained unchanged. Meanwhile, abnormally dry conditions (D0) expanded into central Colorado, southwestern Wyoming, and west-central South Dakota. In areas receiving heavy rain and snow, such as northeastern Kansas and southeastern Nebraska, D0 was eliminated. As more data are collected and analyzed, drought impacts are still being realized in some parts of the region. According to a study by the U.S. Forest Service and Colorado State Forest Survey, the spruce beetle epidemic has expanded due to a combination of factors, one of which is drought. Southwestern areas of the state have experienced the most rapid expansion of the infestation. On a related matter, the mountain pine beetle epidemic has slowed, most likely due to a lack of live trees.

As explained by the Southern Regional Climate Center, February was a cold month for all six states in the Southern region and, with the exception of western Tennessee, the month was a drier than normal month. Conditions were especially dry throughout central Texas, where most stations received half (or less) of the normal precipitation for the month. Similar shortfalls were observed across central Louisiana, southwestern Oklahoma, and southern Mississippi. Elsewhere, precipitation totals ranged between 70 to 90 percent of normal, except for in western Tennessee, where most stations reported values that were near normal to slightly above normal. For Louisiana, it was their twenty-seventh driest February on record (1895-2015). All other state rankings fell within the two middle quartiles.

Drought conditions in the Southern region changed only slightly from the previous month. In southwestern Texas, below normal precipitation led to an introduction of extreme drought. Similarly, persistent dryness in southern Louisiana and southern Mississippi has resulted in an area of moderate drought along the north central Gulf of Mexico coast. Above normal precipitation in western Tennessee has alleviated drought conditions there, however, much of the area is still considered abnormally dry. Elsewhere, conditions have not changed much, with a bulk of the counties in northwestern Texas and western Oklahoma still experiencing severe, extreme and exceptional drought. In Texas, winter wheat and pecans are doing well across the state. Dairy production has increased 2% from the summer months and the number of cattle have increased after hitting a 48-year record low in 2014. Cotton is expected to have a large reduction due to the cold weather, so many farmers have turned to growing sorghum instead. Soil moisture fared better in the South Plains than in the Panhandle where the soil moisture was short to adequate. The counties of Hale and Swisher now have adequate soil moisture after previously suffering from drought conditions. Ecologically, there were more snow geese found in the state than in previous years. Unseasonably warm temperatures for a portion of the month brought out sand bass and other fish for early season fishing. Statewide reservoirs rose nearly a full percent from the beginning of the month, going from 65.0% to 65.9%. In east Texas, most reservoirs are at or near capacity. In the panhandle, north Texas, and southcentral Texas, reservoir levels are running on the low side, which has prompted experts in Austin and Amarillo to deliberate further water conservation solutions (Information provided by the Texas Office of State Climatology).

As summarized by the Midwest Regional Climate Center, February 2015 had some of the coldest temperatures seen in decades, tying the year 1904 as the 7th coldest February on record (1895-2015) for the Midwestern region. February accumulated precipitation across the region remained 0.5 to 1.25 inches (1.3-3.2 cm) below normal except in southeast Kentucky, northern Missouri, most of Iowa, and small areas along Lake Superior and Lake of the Woods which were only 0.25 to 0.5 inch (0.6-1.3 cm) above average. This resulted in a majority of the Midwest region experiencing only 50-75 percent of normal accumulated precipitation, with the entire region experiencing its 28th driest February on record only observing 1.21 inches (3.1 cm), 0.51 inch (1.3 cm) below normal (70 percent of normal).

The region was drier than normal during the 2014-2015 winter season in terms of total accumulated precipitation, with portions of Kentucky and southwest Missouri being 3.0 to 5.0 inches (7.6 to 12.7 cm) below normal. Ohio, Indiana, Illinois, remainder of Missouri, Michigan, eastern Iowa and Minnesota, along with much of Wisconsin were all 1.0 to 3.0 inches (2.5 to 7.6 cm) below normal. The Midwest region observed precipitation during winter 2014-2015 was 4.2 inches (10.7 cm), 1.5 inches (3.8 cm) below normal and the 15th driest winter on record for the Midwest.

D0 drought conditions remained in place across much of Kentucky, primarily west of the Appalachian Mountains. Minnesota remained in D0 drought for the entire month, as little precipitation fell across the state. At the beginning of winter, much of Minnesota and far northwest Iowa were classified as Abnormally Dry on the USDM and remained classified as such through the season. Entering mid-December, western Kentucky and far southeast Missouri joined the ranks of Abnormally Dry. Conditions remained stationary till mid-January when growth of the water shortage in Kentucky spread eastward and reached Moderate Drought status in the far southwest. By January 27, 2015 the lack of precipitation across the region resulted in additional growth of drought conditions: all of Minnesota had been classified as Abnormally Dry with small isolated regions of Moderate Drought, followed by a dry region across southeast Iowa, northern Missouri, northwest Illinois, and southern Wisconsin. Abnormally Dry and Moderate Drought in Kentucky was noted across the state west of the Appalachian Mountains. Following the January 31-February 2, 2015 winter storm across the central Midwest, drought status was removed across Missouri, Iowa, and northwest Illinois. Southern Wisconsin remained in drought status having received little snow from the event. Much of Kentucky reached Moderate drought conditions by February 17th but received relief from additional winter storms so that by March, drought status for the state had been downgraded to Abnormally dry along the northern counties near the Ohio River west of the Indiana and Ohio state line.

As noted by the Southeast Regional Climate Center, precipitation was slightly below normal but highly variable across the Southeast during February. The driest locations were found across northern Virginia, western North Carolina, southern Alabama, and the western tip of the Florida Panhandle. Monthly precipitation totals were 2 to 4 inches (50.8 to 101.6 mm) below normal, or about 50 to 25 percent of normal, in these areas. Precipitation was slightly above normal for much of Puerto Rico and the U.S. Virgin Islands. Mean temperatures in February were well below average across much of the region.

A modest change in drought conditions was noted for the Southeast during February. The percentage of the region under drought-free conditions (less than D1) decreased slightly from 99 percent on the 3rd to 96 percent on the 24th. Moderate (D1) drought expanded northward and eastward from the Mobile Bay area of coastal Alabama during the month, covering the entire southwestern portion of the state as well as the western tip of the Florida Panhandle. Approximately 17 percent of Alabama was under moderate drought conditions by the end of February, which is a significant increase from only 2 percent coverage at the beginning of the month. In addition, a small area of moderate drought developed in the Everglades region of southern Florida. Numerous freeze events during the latter half of the month damaged about 10 to 30 percent of the blueberry crop across portions of southern Georgia.

As explained by the Northeast Regional Climate Center, February ended on the dry side of normal in the Northeast. The region saw 1.92 inches (48.77 mm) of precipitation, 70 percent of normal, which made it the 12th driest February on record. All states were drier than normal, with three states ranking the month among their top 20 driest: Connecticut, 11th driest; Pennsylvania, 13th driest; and Maine, 16th driest. Departures ranged from 56 percent of normal in Massachusetts to 83 percent of normal in West Virginia. Winter also ended on the dry side of normal, but barely. The region saw 8.87 inches (225.30 mm) of precipitation, 96 percent of normal. Six states were wetter than normal, while five states were drier than normal and one state was at normal. Departures for all states ranged from 79 percent of normal in Pennsylvania to 118 percent of normal in Maine. Despite the Northeast generally being drier than normal during February and winter, snowfall was above normal in most areas. According to the USDM, 17 to 18 percent of the region was experiencing abnormally dry conditions throughout the month. February was an extraordinarily cold month in the Northeast. The region's average temperature of 13.5 degrees F (-10.3 degrees C) was 12.7 degrees F (7.1 degrees C) below normal. This made it the 2nd coldest February on record behind 1934, which had an average temperature of 12.0 degrees F (-11.1 degrees C).

As summarized by the Western Regional Climate Center, strong and persistent high pressure anchored over the West this month resulted in a large number of record temperatures in the Sierra Nevada, Great Basin, and Central Rockies. February was the 3rd consecutive month of widespread above normal temperatures in the West, and the 15th consecutive month for the state of California. Precipitation varied widely, having no recognizable pattern across the West, with record February totals in areas of the central and southern Rockies and drier than normal conditions in central and southern California as well as large areas of the Great Basin.

Following a warm and dry start to the month, the second half of February brought cold and snowy conditions to the central and southern Rockies. A series of storms in early February brought beneficial precipitation to northern California and areas of the Pacific Northwest, helping to improve drought conditions in these areas. At the end of the month, severe to exceptional drought persisted in 67% of California, 48% of Nevada, and 34% of Oregon. At month's end, snowpack remained meager in the Cascades, with many locations less than 25% of normal snow water equivalent (SWE). The Sierra Nevada fared slightly better thanks to a cold storm at the end of the month and had SWE values 20-40% of normal. Throughout the Rockies, basin average SWE values ranged from roughly 80-110% of normal.

Warm conditions were observed across Western and Southcentral Alaska as well as the North Slope. In western Alaska, Kotzebue noted an average temperature of 10.2 F (-12.1 C) for the month, 11.1 F (6.2 C) above average and the 3rd warmest February since records began in 1897. Precipitation was highly variable across the state, though generally below normal in the Southcentral and Southeast regions and parts of the Interior. For the snow season to-date (since July 1), Anchorage has only received 20.5 in (52 cm), making this season the 2nd least snowy on record so far. Normal snowfall at Anchorage by the end of February is 60.3 in (153 cm). The famed Iditarod sled race was altered to accommodate the warmth and dryness. Further south, drier than normal conditions prevailed for much of Hawaii. Hilo and Honolulu recorded 55% and 43% of normal, respectively. Lihue, Kauai recorded its 5th driest February on record at 0.75 in (19 mm). At month's end, 50% of the state was experiencing moderate drought.

Pacific Islands: According to reports from National Weather Service offices, the Pacific ENSO Applications Climate Center (PEAC), and partners, conditions varied across the Pacific Islands.

The rainfall amounts at most of the reporting stations were below the minimum thresholds (4 or 8 inches) required to meet most monthly water needs, so February 2015 could be considered to have been a mostly dry month. The 4- and 8-inch thresholds are important because, if monthly precipitation falls below the threshold, then drought becomes a concern. The Mariana Islands have been especially dry, with Guam reporting only 0.18 inch of precipitation — the driest February on record — and Saipan only 0.35 inch. Two of the last three months have been very dry at Guam and Saipan. Kwajalein (with 3.94 inches) was below the 4-inch threshold, with February marking the third consecutive month below the 8-inch threshold. Majuro (with 4.32 inches) was below the 8-inch threshold in February. Koror (with 7.07 inches) and Yap (4.60 inches) were below the 8-inch threshold for the second consecutive month. Chuyuk, Pohnpei, Kosrae, Pago Pago, Luchonoch, and Kapingamarangi were above the 8-inch threshold.
Other stations in Micronesia that reported precipitation totals for February include Fananu (7.39 inches), Nukuoro (6.84 inches), Ulithi (3.72 inches), Ailinglapalap (4.17 inches), Utirik (0.59 inch), and Wotje (0.93 inch), which were all below the 8-inch threshold. The northern Marshall Islands have been especially dry, with Utirik and Wotje receiving less than 4 inches of rain for each of the last three months and less than 8 inches for each of the last five months. Pingelap was wet with 14.13 inches of rain in February.

As measured by percent of normal precipitation, Koror was drier than normal in both the short term (February, year to date [January-February 2015], and three-month time scale [December 2014-February 2015]) and long term (12-month time scale, March 2014-February 2015).
Pohnpei and Kosrae were wetter than normal in February but mostly drier than normal.
Guam, Saipan and Majuro were dry in the short term but wet in the long term.
Kapingamarangi was wet in the short term but dry in the long term.
Chuuk and Pago Pago were wetter than normal at both the short- and long-term time scales.
The precipitation pattern for the other stations varied.